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WGU C785 BIOCHEMISTRY UNIT EXAM QUESTIONS
& ANSWERS LATEST 2026/2027 WITH COMPLETE
SOLUTION
1. A researcher hydrolyzes a protein into individual amino acids by
breaking the covalent bonds that connect adjacent amino acids. Which
level of protein organization is directly disrupted by this reaction?
A. Secondary structure
B. Tertiary structure
C. Primary structure
D. Quaternary structure
Answer: C
Solution: Primary structure is the linear sequence of amino acids joined
by peptide bonds. Hydrolysis breaks these peptide bonds, directly
disrupting the primary structure.
2. A mutation replaces a nonpolar amino acid within the hydrophobic
core of a protein with a highly charged amino acid. Which consequence
is most likely?
A. The mutation can alter folding because the new side chain interacts
differently with its environment.
B. The mutation will have no effect because all amino acids have
equivalent chemical properties.
C. The mutation will automatically create a new peptide bond.
D. The mutation can affect only the protein's primary structure and never
its function.
Answer: A
Solution: Protein folding depends heavily on side-chain chemistry.
Replacing a hydrophobic residue with a charged residue can disrupt
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hydrophobic interactions and alter the protein's three-dimensional
structure and function.
3. Which interaction is primarily responsible for stabilizing the alpha-
helix and beta-pleated-sheet structures of proteins?
A. Peptide bonds between side chains
B. Hydrogen bonding involving backbone groups
C. Covalent bonds between all R groups
D. Phosphodiester bonds
Answer: B
Solution: Secondary protein structure is stabilized primarily by
hydrogen bonds between backbone carbonyl oxygen and amide
hydrogen groups.
4. A protein contains two cysteine residues that form a covalent linkage
between their side chains. Which interaction has formed?
A. Ionic interaction
B. Hydrogen bond
C. Peptide bond
D. Disulfide bond
Answer: D
Solution: Oxidation of two cysteine sulfhydryl groups can produce a
covalent disulfide bond. These bonds contribute to tertiary and, in some
proteins, quaternary structure.
5. A patient has a mutation in the β-globin gene that substitutes valine
for glutamate at a specific position. Why can this seemingly small
substitution substantially alter hemoglobin behavior?
A. Both amino acids have identical side-chain properties.
B. The substitution changes a charged, hydrophilic residue to a nonpolar
residue, potentially altering intermolecular interactions.
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C. The substitution removes every peptide bond in hemoglobin.
D. Valine prevents hemoglobin from containing iron.
Answer: B
Solution: Glutamate is negatively charged at physiological pH, whereas
valine is nonpolar. Changing the side-chain chemistry can alter protein
interactions and contributes to the molecular basis of sickle-cell disease.
6. An enzyme catalyzes a biochemical reaction without being consumed.
Which statement best explains this property?
A. The enzyme changes the equilibrium constant of the reaction.
B. The enzyme provides an alternative pathway with lower activation
energy.
C. The enzyme increases the amount of product that exists at
equilibrium.
D. The enzyme permanently changes into the product.
Answer: B
Solution: Enzymes accelerate reactions by lowering activation energy.
They are regenerated during the reaction and do not alter the reaction's
overall equilibrium.
7. An enzyme has reached its maximum reaction velocity because every
available active site is occupied by substrate. What would most directly
increase the reaction rate at this point?
A. Increasing enzyme concentration
B. Decreasing substrate concentration
C. Removing all cofactors
D. Adding a competitive inhibitor
Answer: A
Solution: When substrate is saturating, additional substrate produces
little further increase in velocity. Increasing the amount of enzyme
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provides additional active sites and can increase the maximum reaction
rate.
8. A competitive inhibitor is added to an enzyme-catalyzed reaction.
Which mechanism best describes the inhibitor's action?
A. It binds irreversibly to a site unrelated to the active site in every case.
B. It competes with substrate for access to the enzyme's active site.
C. It permanently increases enzyme activity.
D. It converts substrate directly into product.
Answer: B
Solution: Competitive inhibitors resemble or compete with the substrate
for the active site. Increasing substrate concentration can often overcome
competitive inhibition.
9. A patient develops a fever of 41°C, and an enzyme-dependent
metabolic pathway begins functioning poorly. Which explanation is
most appropriate?
A. High temperature can disrupt weak interactions that maintain protein
structure, potentially causing denaturation.
B. High temperature always increases enzyme activity indefinitely.
C. Temperature has no effect on protein structure.
D. High temperature converts proteins directly into carbohydrates.
Answer: A
Solution: Enzymes have optimal temperature ranges. Excessive heat can
disrupt hydrogen bonds and other noncovalent interactions, altering the
enzyme's three-dimensional structure and active site.
10. A biochemical reaction requires a molecule that binds to an enzyme
and is essential for catalytic activity but is not itself a protein. Which
term best describes this molecule?
A. Cofactor or coenzyme
B. Structural lipid
WGU C785 BIOCHEMISTRY UNIT EXAM QUESTIONS
& ANSWERS LATEST 2026/2027 WITH COMPLETE
SOLUTION
1. A researcher hydrolyzes a protein into individual amino acids by
breaking the covalent bonds that connect adjacent amino acids. Which
level of protein organization is directly disrupted by this reaction?
A. Secondary structure
B. Tertiary structure
C. Primary structure
D. Quaternary structure
Answer: C
Solution: Primary structure is the linear sequence of amino acids joined
by peptide bonds. Hydrolysis breaks these peptide bonds, directly
disrupting the primary structure.
2. A mutation replaces a nonpolar amino acid within the hydrophobic
core of a protein with a highly charged amino acid. Which consequence
is most likely?
A. The mutation can alter folding because the new side chain interacts
differently with its environment.
B. The mutation will have no effect because all amino acids have
equivalent chemical properties.
C. The mutation will automatically create a new peptide bond.
D. The mutation can affect only the protein's primary structure and never
its function.
Answer: A
Solution: Protein folding depends heavily on side-chain chemistry.
Replacing a hydrophobic residue with a charged residue can disrupt
,2|Page
hydrophobic interactions and alter the protein's three-dimensional
structure and function.
3. Which interaction is primarily responsible for stabilizing the alpha-
helix and beta-pleated-sheet structures of proteins?
A. Peptide bonds between side chains
B. Hydrogen bonding involving backbone groups
C. Covalent bonds between all R groups
D. Phosphodiester bonds
Answer: B
Solution: Secondary protein structure is stabilized primarily by
hydrogen bonds between backbone carbonyl oxygen and amide
hydrogen groups.
4. A protein contains two cysteine residues that form a covalent linkage
between their side chains. Which interaction has formed?
A. Ionic interaction
B. Hydrogen bond
C. Peptide bond
D. Disulfide bond
Answer: D
Solution: Oxidation of two cysteine sulfhydryl groups can produce a
covalent disulfide bond. These bonds contribute to tertiary and, in some
proteins, quaternary structure.
5. A patient has a mutation in the β-globin gene that substitutes valine
for glutamate at a specific position. Why can this seemingly small
substitution substantially alter hemoglobin behavior?
A. Both amino acids have identical side-chain properties.
B. The substitution changes a charged, hydrophilic residue to a nonpolar
residue, potentially altering intermolecular interactions.
,3|Page
C. The substitution removes every peptide bond in hemoglobin.
D. Valine prevents hemoglobin from containing iron.
Answer: B
Solution: Glutamate is negatively charged at physiological pH, whereas
valine is nonpolar. Changing the side-chain chemistry can alter protein
interactions and contributes to the molecular basis of sickle-cell disease.
6. An enzyme catalyzes a biochemical reaction without being consumed.
Which statement best explains this property?
A. The enzyme changes the equilibrium constant of the reaction.
B. The enzyme provides an alternative pathway with lower activation
energy.
C. The enzyme increases the amount of product that exists at
equilibrium.
D. The enzyme permanently changes into the product.
Answer: B
Solution: Enzymes accelerate reactions by lowering activation energy.
They are regenerated during the reaction and do not alter the reaction's
overall equilibrium.
7. An enzyme has reached its maximum reaction velocity because every
available active site is occupied by substrate. What would most directly
increase the reaction rate at this point?
A. Increasing enzyme concentration
B. Decreasing substrate concentration
C. Removing all cofactors
D. Adding a competitive inhibitor
Answer: A
Solution: When substrate is saturating, additional substrate produces
little further increase in velocity. Increasing the amount of enzyme
, 4|Page
provides additional active sites and can increase the maximum reaction
rate.
8. A competitive inhibitor is added to an enzyme-catalyzed reaction.
Which mechanism best describes the inhibitor's action?
A. It binds irreversibly to a site unrelated to the active site in every case.
B. It competes with substrate for access to the enzyme's active site.
C. It permanently increases enzyme activity.
D. It converts substrate directly into product.
Answer: B
Solution: Competitive inhibitors resemble or compete with the substrate
for the active site. Increasing substrate concentration can often overcome
competitive inhibition.
9. A patient develops a fever of 41°C, and an enzyme-dependent
metabolic pathway begins functioning poorly. Which explanation is
most appropriate?
A. High temperature can disrupt weak interactions that maintain protein
structure, potentially causing denaturation.
B. High temperature always increases enzyme activity indefinitely.
C. Temperature has no effect on protein structure.
D. High temperature converts proteins directly into carbohydrates.
Answer: A
Solution: Enzymes have optimal temperature ranges. Excessive heat can
disrupt hydrogen bonds and other noncovalent interactions, altering the
enzyme's three-dimensional structure and active site.
10. A biochemical reaction requires a molecule that binds to an enzyme
and is essential for catalytic activity but is not itself a protein. Which
term best describes this molecule?
A. Cofactor or coenzyme
B. Structural lipid
